Mixers are at the heart of radio transmitters and receivers. A mixer ideally combines the signals from two frequency sources to generate an output signal having the sum and differences of the input frequencies. In practice, mixers also generate signals at spurious frequencies.
Modern radio designers typically utilize circuit simulators in the design of circuits that utilize mixers. However, a satisfactory model for representing mixers in such simulators is not available. At present, mixers are simulated utilizing mixer Inter-Modulation Table (IMT) methods. The existing mixer IMT models map each input frequency to multiple output frequencies using a table look-up approach. The mixer IMT data can be measured with a spectrum analyzer, or be generated with a nonlinear circuit simulator for any particular mixer design.
This approach has several drawbacks. It is not applicable to time domain simulators. In addition, it does not model adjacent channel power in circuit envelope simulators. Further, it does not model inter-modulation among multiple input tones in harmonic balance simulators. Finally, it does not model noise mapping in harmonic balance simulators and circuit envelope simulators.
Broadly, it is the object of the present invention to provide an improved method for modeling mixers that is applicable to a wider range of simulators than the existing mixer IMT models.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.